LoopInfo.h revision 16a2c927e95c29a316d0271c93e0490ce3bc06ce
1//===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator -------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file defines the LoopInfo class that is used to identify natural loops 11// and determine the loop depth of various nodes of the CFG. Note that natural 12// loops may actually be several loops that share the same header node. 13// 14// This analysis calculates the nesting structure of loops in a function. For 15// each natural loop identified, this analysis identifies natural loops 16// contained entirely within the loop and the basic blocks the make up the loop. 17// 18// It can calculate on the fly various bits of information, for example: 19// 20// * whether there is a preheader for the loop 21// * the number of back edges to the header 22// * whether or not a particular block branches out of the loop 23// * the successor blocks of the loop 24// * the loop depth 25// * the trip count 26// * etc... 27// 28//===----------------------------------------------------------------------===// 29 30#ifndef LLVM_ANALYSIS_LOOP_INFO_H 31#define LLVM_ANALYSIS_LOOP_INFO_H 32 33#include "llvm/Pass.h" 34#include "llvm/ADT/DepthFirstIterator.h" 35#include "llvm/ADT/GraphTraits.h" 36#include "llvm/ADT/SmallVector.h" 37#include "llvm/Analysis/Dominators.h" 38#include "llvm/Support/CFG.h" 39#include "llvm/Support/Streams.h" 40#include <algorithm> 41#include <ostream> 42 43namespace llvm { 44 45template<typename T> 46static void RemoveFromVector(std::vector<T*> &V, T *N) { 47 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N); 48 assert(I != V.end() && "N is not in this list!"); 49 V.erase(I); 50} 51 52class DominatorTree; 53class LoopInfo; 54class Loop; 55template<class N, class M> class LoopInfoBase; 56template<class N, class M> class LoopBase; 57 58//===----------------------------------------------------------------------===// 59/// LoopBase class - Instances of this class are used to represent loops that 60/// are detected in the flow graph 61/// 62template<class BlockT, class LoopT> 63class LoopBase { 64 LoopT *ParentLoop; 65 // SubLoops - Loops contained entirely within this one. 66 std::vector<LoopT *> SubLoops; 67 68 // Blocks - The list of blocks in this loop. First entry is the header node. 69 std::vector<BlockT*> Blocks; 70 71 // DO NOT IMPLEMENT 72 LoopBase(const LoopBase<BlockT, LoopT> &); 73 // DO NOT IMPLEMENT 74 const LoopBase<BlockT, LoopT>&operator=(const LoopBase<BlockT, LoopT> &); 75public: 76 /// Loop ctor - This creates an empty loop. 77 LoopBase() : ParentLoop(0) {} 78 ~LoopBase() { 79 for (size_t i = 0, e = SubLoops.size(); i != e; ++i) 80 delete SubLoops[i]; 81 } 82 83 /// getLoopDepth - Return the nesting level of this loop. An outer-most 84 /// loop has depth 1, for consistency with loop depth values used for basic 85 /// blocks, where depth 0 is used for blocks not inside any loops. 86 unsigned getLoopDepth() const { 87 unsigned D = 1; 88 for (const LoopT *CurLoop = ParentLoop; CurLoop; 89 CurLoop = CurLoop->ParentLoop) 90 ++D; 91 return D; 92 } 93 BlockT *getHeader() const { return Blocks.front(); } 94 LoopT *getParentLoop() const { return ParentLoop; } 95 96 /// contains - Return true if the specified basic block is in this loop 97 /// 98 bool contains(const BlockT *BB) const { 99 return std::find(block_begin(), block_end(), BB) != block_end(); 100 } 101 102 /// iterator/begin/end - Return the loops contained entirely within this loop. 103 /// 104 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; } 105 typedef typename std::vector<LoopT *>::const_iterator iterator; 106 iterator begin() const { return SubLoops.begin(); } 107 iterator end() const { return SubLoops.end(); } 108 bool empty() const { return SubLoops.empty(); } 109 110 /// getBlocks - Get a list of the basic blocks which make up this loop. 111 /// 112 const std::vector<BlockT*> &getBlocks() const { return Blocks; } 113 typedef typename std::vector<BlockT*>::const_iterator block_iterator; 114 block_iterator block_begin() const { return Blocks.begin(); } 115 block_iterator block_end() const { return Blocks.end(); } 116 117 /// isLoopExit - True if terminator in the block can branch to another block 118 /// that is outside of the current loop. 119 /// 120 bool isLoopExit(const BlockT *BB) const { 121 typedef GraphTraits<BlockT*> BlockTraits; 122 for (typename BlockTraits::ChildIteratorType SI = 123 BlockTraits::child_begin(const_cast<BlockT*>(BB)), 124 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) { 125 if (!contains(*SI)) 126 return true; 127 } 128 return false; 129 } 130 131 /// getNumBackEdges - Calculate the number of back edges to the loop header 132 /// 133 unsigned getNumBackEdges() const { 134 unsigned NumBackEdges = 0; 135 BlockT *H = getHeader(); 136 137 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 138 for (typename InvBlockTraits::ChildIteratorType I = 139 InvBlockTraits::child_begin(const_cast<BlockT*>(H)), 140 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I) 141 if (contains(*I)) 142 ++NumBackEdges; 143 144 return NumBackEdges; 145 } 146 147 //===--------------------------------------------------------------------===// 148 // APIs for simple analysis of the loop. 149 // 150 // Note that all of these methods can fail on general loops (ie, there may not 151 // be a preheader, etc). For best success, the loop simplification and 152 // induction variable canonicalization pass should be used to normalize loops 153 // for easy analysis. These methods assume canonical loops. 154 155 /// getExitingBlocks - Return all blocks inside the loop that have successors 156 /// outside of the loop. These are the blocks _inside of the current loop_ 157 /// which branch out. The returned list is always unique. 158 /// 159 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const { 160 // Sort the blocks vector so that we can use binary search to do quick 161 // lookups. 162 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 163 std::sort(LoopBBs.begin(), LoopBBs.end()); 164 165 typedef GraphTraits<BlockT*> BlockTraits; 166 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 167 for (typename BlockTraits::ChildIteratorType I = 168 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 169 I != E; ++I) 170 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) { 171 // Not in current loop? It must be an exit block. 172 ExitingBlocks.push_back(*BI); 173 break; 174 } 175 } 176 177 /// getExitingBlock - If getExitingBlocks would return exactly one block, 178 /// return that block. Otherwise return null. 179 BlockT *getExitingBlock() const { 180 SmallVector<BlockT*, 8> ExitingBlocks; 181 getExitingBlocks(ExitingBlocks); 182 if (ExitingBlocks.size() == 1) 183 return ExitingBlocks[0]; 184 return 0; 185 } 186 187 /// getExitBlocks - Return all of the successor blocks of this loop. These 188 /// are the blocks _outside of the current loop_ which are branched to. 189 /// 190 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const { 191 // Sort the blocks vector so that we can use binary search to do quick 192 // lookups. 193 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 194 std::sort(LoopBBs.begin(), LoopBBs.end()); 195 196 typedef GraphTraits<BlockT*> BlockTraits; 197 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 198 for (typename BlockTraits::ChildIteratorType I = 199 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 200 I != E; ++I) 201 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 202 // Not in current loop? It must be an exit block. 203 ExitBlocks.push_back(*I); 204 } 205 206 /// getExitBlock - If getExitBlocks would return exactly one block, 207 /// return that block. Otherwise return null. 208 BlockT *getExitBlock() const { 209 SmallVector<BlockT*, 8> ExitBlocks; 210 getExitBlocks(ExitBlocks); 211 if (ExitBlocks.size() == 1) 212 return ExitBlocks[0]; 213 return 0; 214 } 215 216 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 217 /// These are the blocks _outside of the current loop_ which are branched to. 218 /// This assumes that loop is in canonical form. 219 /// 220 void getUniqueExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const { 221 // Sort the blocks vector so that we can use binary search to do quick 222 // lookups. 223 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 224 std::sort(LoopBBs.begin(), LoopBBs.end()); 225 226 std::vector<BlockT*> switchExitBlocks; 227 228 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) { 229 230 BlockT *current = *BI; 231 switchExitBlocks.clear(); 232 233 typedef GraphTraits<BlockT*> BlockTraits; 234 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 235 for (typename BlockTraits::ChildIteratorType I = 236 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 237 I != E; ++I) { 238 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 239 // If block is inside the loop then it is not a exit block. 240 continue; 241 242 typename InvBlockTraits::ChildIteratorType PI = 243 InvBlockTraits::child_begin(*I); 244 BlockT *firstPred = *PI; 245 246 // If current basic block is this exit block's first predecessor 247 // then only insert exit block in to the output ExitBlocks vector. 248 // This ensures that same exit block is not inserted twice into 249 // ExitBlocks vector. 250 if (current != firstPred) 251 continue; 252 253 // If a terminator has more then two successors, for example SwitchInst, 254 // then it is possible that there are multiple edges from current block 255 // to one exit block. 256 if (std::distance(BlockTraits::child_begin(current), 257 BlockTraits::child_end(current)) <= 2) { 258 ExitBlocks.push_back(*I); 259 continue; 260 } 261 262 // In case of multiple edges from current block to exit block, collect 263 // only one edge in ExitBlocks. Use switchExitBlocks to keep track of 264 // duplicate edges. 265 if (std::find(switchExitBlocks.begin(), switchExitBlocks.end(), *I) 266 == switchExitBlocks.end()) { 267 switchExitBlocks.push_back(*I); 268 ExitBlocks.push_back(*I); 269 } 270 } 271 } 272 } 273 274 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one 275 /// block, return that block. Otherwise return null. 276 BlockT *getUniqueExitBlock() const { 277 SmallVector<BlockT*, 8> UniqueExitBlocks; 278 getUniqueExitBlocks(UniqueExitBlocks); 279 if (UniqueExitBlocks.size() == 1) 280 return UniqueExitBlocks[0]; 281 return 0; 282 } 283 284 /// getLoopPreheader - If there is a preheader for this loop, return it. A 285 /// loop has a preheader if there is only one edge to the header of the loop 286 /// from outside of the loop. If this is the case, the block branching to the 287 /// header of the loop is the preheader node. 288 /// 289 /// This method returns null if there is no preheader for the loop. 290 /// 291 BlockT *getLoopPreheader() const { 292 // Keep track of nodes outside the loop branching to the header... 293 BlockT *Out = 0; 294 295 // Loop over the predecessors of the header node... 296 BlockT *Header = getHeader(); 297 typedef GraphTraits<BlockT*> BlockTraits; 298 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 299 for (typename InvBlockTraits::ChildIteratorType PI = 300 InvBlockTraits::child_begin(Header), 301 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) 302 if (!contains(*PI)) { // If the block is not in the loop... 303 if (Out && Out != *PI) 304 return 0; // Multiple predecessors outside the loop 305 Out = *PI; 306 } 307 308 // Make sure there is only one exit out of the preheader. 309 assert(Out && "Header of loop has no predecessors from outside loop?"); 310 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); 311 ++SI; 312 if (SI != BlockTraits::child_end(Out)) 313 return 0; // Multiple exits from the block, must not be a preheader. 314 315 // If there is exactly one preheader, return it. If there was zero, then 316 // Out is still null. 317 return Out; 318 } 319 320 /// getLoopLatch - If there is a single latch block for this loop, return it. 321 /// A latch block is a block that contains a branch back to the header. 322 /// A loop header in normal form has two edges into it: one from a preheader 323 /// and one from a latch block. 324 BlockT *getLoopLatch() const { 325 BlockT *Header = getHeader(); 326 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 327 typename InvBlockTraits::ChildIteratorType PI = 328 InvBlockTraits::child_begin(Header); 329 typename InvBlockTraits::ChildIteratorType PE = 330 InvBlockTraits::child_end(Header); 331 if (PI == PE) return 0; // no preds? 332 333 BlockT *Latch = 0; 334 if (contains(*PI)) 335 Latch = *PI; 336 ++PI; 337 if (PI == PE) return 0; // only one pred? 338 339 if (contains(*PI)) { 340 if (Latch) return 0; // multiple backedges 341 Latch = *PI; 342 } 343 ++PI; 344 if (PI != PE) return 0; // more than two preds 345 346 return Latch; 347 } 348 349 //===--------------------------------------------------------------------===// 350 // APIs for updating loop information after changing the CFG 351 // 352 353 /// addBasicBlockToLoop - This method is used by other analyses to update loop 354 /// information. NewBB is set to be a new member of the current loop. 355 /// Because of this, it is added as a member of all parent loops, and is added 356 /// to the specified LoopInfo object as being in the current basic block. It 357 /// is not valid to replace the loop header with this method. 358 /// 359 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI); 360 361 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 362 /// the OldChild entry in our children list with NewChild, and updates the 363 /// parent pointer of OldChild to be null and the NewChild to be this loop. 364 /// This updates the loop depth of the new child. 365 void replaceChildLoopWith(LoopT *OldChild, 366 LoopT *NewChild) { 367 assert(OldChild->ParentLoop == this && "This loop is already broken!"); 368 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 369 typename std::vector<LoopT *>::iterator I = 370 std::find(SubLoops.begin(), SubLoops.end(), OldChild); 371 assert(I != SubLoops.end() && "OldChild not in loop!"); 372 *I = NewChild; 373 OldChild->ParentLoop = 0; 374 NewChild->ParentLoop = static_cast<LoopT *>(this); 375 } 376 377 /// addChildLoop - Add the specified loop to be a child of this loop. This 378 /// updates the loop depth of the new child. 379 /// 380 void addChildLoop(LoopT *NewChild) { 381 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 382 NewChild->ParentLoop = static_cast<LoopT *>(this); 383 SubLoops.push_back(NewChild); 384 } 385 386 /// removeChildLoop - This removes the specified child from being a subloop of 387 /// this loop. The loop is not deleted, as it will presumably be inserted 388 /// into another loop. 389 LoopT *removeChildLoop(iterator I) { 390 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 391 LoopT *Child = *I; 392 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 393 SubLoops.erase(SubLoops.begin()+(I-begin())); 394 Child->ParentLoop = 0; 395 return Child; 396 } 397 398 /// addBlockEntry - This adds a basic block directly to the basic block list. 399 /// This should only be used by transformations that create new loops. Other 400 /// transformations should use addBasicBlockToLoop. 401 void addBlockEntry(BlockT *BB) { 402 Blocks.push_back(BB); 403 } 404 405 /// moveToHeader - This method is used to move BB (which must be part of this 406 /// loop) to be the loop header of the loop (the block that dominates all 407 /// others). 408 void moveToHeader(BlockT *BB) { 409 if (Blocks[0] == BB) return; 410 for (unsigned i = 0; ; ++i) { 411 assert(i != Blocks.size() && "Loop does not contain BB!"); 412 if (Blocks[i] == BB) { 413 Blocks[i] = Blocks[0]; 414 Blocks[0] = BB; 415 return; 416 } 417 } 418 } 419 420 /// removeBlockFromLoop - This removes the specified basic block from the 421 /// current loop, updating the Blocks as appropriate. This does not update 422 /// the mapping in the LoopInfo class. 423 void removeBlockFromLoop(BlockT *BB) { 424 RemoveFromVector(Blocks, BB); 425 } 426 427 /// verifyLoop - Verify loop structure 428 void verifyLoop() const { 429#ifndef NDEBUG 430 assert (getHeader() && "Loop header is missing"); 431 assert (getLoopPreheader() && "Loop preheader is missing"); 432 assert (getLoopLatch() && "Loop latch is missing"); 433 for (iterator I = SubLoops.begin(), E = SubLoops.end(); I != E; ++I) 434 (*I)->verifyLoop(); 435#endif 436 } 437 438 void print(std::ostream &OS, unsigned Depth = 0) const { 439 OS << std::string(Depth*2, ' ') << "Loop at depth " << getLoopDepth() 440 << " containing: "; 441 442 for (unsigned i = 0; i < getBlocks().size(); ++i) { 443 if (i) OS << ","; 444 BlockT *BB = getBlocks()[i]; 445 WriteAsOperand(OS, BB, false); 446 if (BB == getHeader()) OS << "<header>"; 447 if (BB == getLoopLatch()) OS << "<latch>"; 448 if (isLoopExit(BB)) OS << "<exit>"; 449 } 450 OS << "\n"; 451 452 for (iterator I = begin(), E = end(); I != E; ++I) 453 (*I)->print(OS, Depth+2); 454 } 455 456 void print(std::ostream *O, unsigned Depth = 0) const { 457 if (O) print(*O, Depth); 458 } 459 460 void dump() const { 461 print(cerr); 462 } 463 464protected: 465 friend class LoopInfoBase<BlockT, LoopT>; 466 explicit LoopBase(BlockT *BB) : ParentLoop(0) { 467 Blocks.push_back(BB); 468 } 469}; 470 471class Loop : public LoopBase<BasicBlock, Loop> { 472public: 473 Loop() {} 474 475 /// isLoopInvariant - Return true if the specified value is loop invariant 476 /// 477 bool isLoopInvariant(Value *V) const; 478 479 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 480 /// induction variable: an integer recurrence that starts at 0 and increments 481 /// by one each time through the loop. If so, return the phi node that 482 /// corresponds to it. 483 /// 484 /// The IndVarSimplify pass transforms loops to have a canonical induction 485 /// variable. 486 /// 487 PHINode *getCanonicalInductionVariable() const; 488 489 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 490 /// the canonical induction variable value for the "next" iteration of the 491 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 492 /// 493 Instruction *getCanonicalInductionVariableIncrement() const; 494 495 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 496 /// times the loop will be executed. Note that this means that the backedge 497 /// of the loop executes N-1 times. If the trip-count cannot be determined, 498 /// this returns null. 499 /// 500 /// The IndVarSimplify pass transforms loops to have a form that this 501 /// function easily understands. 502 /// 503 Value *getTripCount() const; 504 505 /// getSmallConstantTripCount - Returns the trip count of this loop as a 506 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown 507 /// of not constant. Will also return 0 if the trip count is very large 508 /// (>= 2^32) 509 unsigned getSmallConstantTripCount() const; 510 511 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the 512 /// trip count of this loop as a normal unsigned value, if possible. This 513 /// means that the actual trip count is always a multiple of the returned 514 /// value (don't forget the trip count could very well be zero as well!). 515 /// 516 /// Returns 1 if the trip count is unknown or not guaranteed to be the 517 /// multiple of a constant (which is also the case if the trip count is simply 518 /// constant, use getSmallConstantTripCount for that case), Will also return 1 519 /// if the trip count is very large (>= 2^32). 520 unsigned getSmallConstantTripMultiple() const; 521 522 /// isLCSSAForm - Return true if the Loop is in LCSSA form 523 bool isLCSSAForm() const; 524 525private: 526 friend class LoopInfoBase<BasicBlock, Loop>; 527 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} 528}; 529 530//===----------------------------------------------------------------------===// 531/// LoopInfo - This class builds and contains all of the top level loop 532/// structures in the specified function. 533/// 534 535template<class BlockT, class LoopT> 536class LoopInfoBase { 537 // BBMap - Mapping of basic blocks to the inner most loop they occur in 538 std::map<BlockT *, LoopT *> BBMap; 539 std::vector<LoopT *> TopLevelLoops; 540 friend class LoopBase<BlockT, LoopT>; 541 542 void operator=(const LoopInfoBase &); // do not implement 543 LoopInfoBase(const LoopInfo &); // do not implement 544public: 545 LoopInfoBase() { } 546 ~LoopInfoBase() { releaseMemory(); } 547 548 void releaseMemory() { 549 for (typename std::vector<LoopT *>::iterator I = 550 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 551 delete *I; // Delete all of the loops... 552 553 BBMap.clear(); // Reset internal state of analysis 554 TopLevelLoops.clear(); 555 } 556 557 /// iterator/begin/end - The interface to the top-level loops in the current 558 /// function. 559 /// 560 typedef typename std::vector<LoopT *>::const_iterator iterator; 561 iterator begin() const { return TopLevelLoops.begin(); } 562 iterator end() const { return TopLevelLoops.end(); } 563 bool empty() const { return TopLevelLoops.empty(); } 564 565 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 566 /// block is in no loop (for example the entry node), null is returned. 567 /// 568 LoopT *getLoopFor(const BlockT *BB) const { 569 typename std::map<BlockT *, LoopT *>::const_iterator I= 570 BBMap.find(const_cast<BlockT*>(BB)); 571 return I != BBMap.end() ? I->second : 0; 572 } 573 574 /// operator[] - same as getLoopFor... 575 /// 576 const LoopT *operator[](const BlockT *BB) const { 577 return getLoopFor(BB); 578 } 579 580 /// getLoopDepth - Return the loop nesting level of the specified block. A 581 /// depth of 0 means the block is not inside any loop. 582 /// 583 unsigned getLoopDepth(const BlockT *BB) const { 584 const LoopT *L = getLoopFor(BB); 585 return L ? L->getLoopDepth() : 0; 586 } 587 588 // isLoopHeader - True if the block is a loop header node 589 bool isLoopHeader(BlockT *BB) const { 590 const LoopT *L = getLoopFor(BB); 591 return L && L->getHeader() == BB; 592 } 593 594 /// removeLoop - This removes the specified top-level loop from this loop info 595 /// object. The loop is not deleted, as it will presumably be inserted into 596 /// another loop. 597 LoopT *removeLoop(iterator I) { 598 assert(I != end() && "Cannot remove end iterator!"); 599 LoopT *L = *I; 600 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 601 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 602 return L; 603 } 604 605 /// changeLoopFor - Change the top-level loop that contains BB to the 606 /// specified loop. This should be used by transformations that restructure 607 /// the loop hierarchy tree. 608 void changeLoopFor(BlockT *BB, LoopT *L) { 609 LoopT *&OldLoop = BBMap[BB]; 610 assert(OldLoop && "Block not in a loop yet!"); 611 OldLoop = L; 612 } 613 614 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 615 /// list with the indicated loop. 616 void changeTopLevelLoop(LoopT *OldLoop, 617 LoopT *NewLoop) { 618 typename std::vector<LoopT *>::iterator I = 619 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 620 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 621 *I = NewLoop; 622 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 623 "Loops already embedded into a subloop!"); 624 } 625 626 /// addTopLevelLoop - This adds the specified loop to the collection of 627 /// top-level loops. 628 void addTopLevelLoop(LoopT *New) { 629 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 630 TopLevelLoops.push_back(New); 631 } 632 633 /// removeBlock - This method completely removes BB from all data structures, 634 /// including all of the Loop objects it is nested in and our mapping from 635 /// BasicBlocks to loops. 636 void removeBlock(BlockT *BB) { 637 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB); 638 if (I != BBMap.end()) { 639 for (LoopT *L = I->second; L; L = L->getParentLoop()) 640 L->removeBlockFromLoop(BB); 641 642 BBMap.erase(I); 643 } 644 } 645 646 // Internals 647 648 static bool isNotAlreadyContainedIn(const LoopT *SubLoop, 649 const LoopT *ParentLoop) { 650 if (SubLoop == 0) return true; 651 if (SubLoop == ParentLoop) return false; 652 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 653 } 654 655 void Calculate(DominatorTreeBase<BlockT> &DT) { 656 BlockT *RootNode = DT.getRootNode()->getBlock(); 657 658 for (df_iterator<BlockT*> NI = df_begin(RootNode), 659 NE = df_end(RootNode); NI != NE; ++NI) 660 if (LoopT *L = ConsiderForLoop(*NI, DT)) 661 TopLevelLoops.push_back(L); 662 } 663 664 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) { 665 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node? 666 667 std::vector<BlockT *> TodoStack; 668 669 // Scan the predecessors of BB, checking to see if BB dominates any of 670 // them. This identifies backedges which target this node... 671 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 672 for (typename InvBlockTraits::ChildIteratorType I = 673 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); 674 I != E; ++I) 675 if (DT.dominates(BB, *I)) // If BB dominates it's predecessor... 676 TodoStack.push_back(*I); 677 678 if (TodoStack.empty()) return 0; // No backedges to this block... 679 680 // Create a new loop to represent this basic block... 681 LoopT *L = new LoopT(BB); 682 BBMap[BB] = L; 683 684 BlockT *EntryBlock = BB->getParent()->begin(); 685 686 while (!TodoStack.empty()) { // Process all the nodes in the loop 687 BlockT *X = TodoStack.back(); 688 TodoStack.pop_back(); 689 690 if (!L->contains(X) && // As of yet unprocessed?? 691 DT.dominates(EntryBlock, X)) { // X is reachable from entry block? 692 // Check to see if this block already belongs to a loop. If this occurs 693 // then we have a case where a loop that is supposed to be a child of 694 // the current loop was processed before the current loop. When this 695 // occurs, this child loop gets added to a part of the current loop, 696 // making it a sibling to the current loop. We have to reparent this 697 // loop. 698 if (LoopT *SubLoop = 699 const_cast<LoopT *>(getLoopFor(X))) 700 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ 701 // Remove the subloop from it's current parent... 702 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); 703 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent 704 typename std::vector<LoopT *>::iterator I = 705 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); 706 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?"); 707 SLP->SubLoops.erase(I); // Remove from parent... 708 709 // Add the subloop to THIS loop... 710 SubLoop->ParentLoop = L; 711 L->SubLoops.push_back(SubLoop); 712 } 713 714 // Normal case, add the block to our loop... 715 L->Blocks.push_back(X); 716 717 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 718 719 // Add all of the predecessors of X to the end of the work stack... 720 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), 721 InvBlockTraits::child_end(X)); 722 } 723 } 724 725 // If there are any loops nested within this loop, create them now! 726 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 727 E = L->Blocks.end(); I != E; ++I) 728 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) { 729 L->SubLoops.push_back(NewLoop); 730 NewLoop->ParentLoop = L; 731 } 732 733 // Add the basic blocks that comprise this loop to the BBMap so that this 734 // loop can be found for them. 735 // 736 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 737 E = L->Blocks.end(); I != E; ++I) { 738 typename std::map<BlockT*, LoopT *>::iterator BBMI = BBMap.find(*I); 739 if (BBMI == BBMap.end()) // Not in map yet... 740 BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level 741 } 742 743 // Now that we have a list of all of the child loops of this loop, check to 744 // see if any of them should actually be nested inside of each other. We 745 // can accidentally pull loops our of their parents, so we must make sure to 746 // organize the loop nests correctly now. 747 { 748 std::map<BlockT *, LoopT *> ContainingLoops; 749 for (unsigned i = 0; i != L->SubLoops.size(); ++i) { 750 LoopT *Child = L->SubLoops[i]; 751 assert(Child->getParentLoop() == L && "Not proper child loop?"); 752 753 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) { 754 // If there is already a loop which contains this loop, move this loop 755 // into the containing loop. 756 MoveSiblingLoopInto(Child, ContainingLoop); 757 --i; // The loop got removed from the SubLoops list. 758 } else { 759 // This is currently considered to be a top-level loop. Check to see 760 // if any of the contained blocks are loop headers for subloops we 761 // have already processed. 762 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { 763 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]]; 764 if (BlockLoop == 0) { // Child block not processed yet... 765 BlockLoop = Child; 766 } else if (BlockLoop != Child) { 767 LoopT *SubLoop = BlockLoop; 768 // Reparent all of the blocks which used to belong to BlockLoops 769 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j) 770 ContainingLoops[SubLoop->Blocks[j]] = Child; 771 772 // There is already a loop which contains this block, that means 773 // that we should reparent the loop which the block is currently 774 // considered to belong to to be a child of this loop. 775 MoveSiblingLoopInto(SubLoop, Child); 776 --i; // We just shrunk the SubLoops list. 777 } 778 } 779 } 780 } 781 } 782 783 return L; 784 } 785 786 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside 787 /// of the NewParent Loop, instead of being a sibling of it. 788 void MoveSiblingLoopInto(LoopT *NewChild, 789 LoopT *NewParent) { 790 LoopT *OldParent = NewChild->getParentLoop(); 791 assert(OldParent && OldParent == NewParent->getParentLoop() && 792 NewChild != NewParent && "Not sibling loops!"); 793 794 // Remove NewChild from being a child of OldParent 795 typename std::vector<LoopT *>::iterator I = 796 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), 797 NewChild); 798 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); 799 OldParent->SubLoops.erase(I); // Remove from parent's subloops list 800 NewChild->ParentLoop = 0; 801 802 InsertLoopInto(NewChild, NewParent); 803 } 804 805 /// InsertLoopInto - This inserts loop L into the specified parent loop. If 806 /// the parent loop contains a loop which should contain L, the loop gets 807 /// inserted into L instead. 808 void InsertLoopInto(LoopT *L, LoopT *Parent) { 809 BlockT *LHeader = L->getHeader(); 810 assert(Parent->contains(LHeader) && 811 "This loop should not be inserted here!"); 812 813 // Check to see if it belongs in a child loop... 814 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size()); 815 i != e; ++i) 816 if (Parent->SubLoops[i]->contains(LHeader)) { 817 InsertLoopInto(L, Parent->SubLoops[i]); 818 return; 819 } 820 821 // If not, insert it here! 822 Parent->SubLoops.push_back(L); 823 L->ParentLoop = Parent; 824 } 825 826 // Debugging 827 828 void print(std::ostream &OS, const Module* ) const { 829 for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 830 TopLevelLoops[i]->print(OS); 831 #if 0 832 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(), 833 E = BBMap.end(); I != E; ++I) 834 OS << "BB '" << I->first->getName() << "' level = " 835 << I->second->getLoopDepth() << "\n"; 836 #endif 837 } 838}; 839 840class LoopInfo : public FunctionPass { 841 LoopInfoBase<BasicBlock, Loop> LI; 842 friend class LoopBase<BasicBlock, Loop>; 843 844 void operator=(const LoopInfo &); // do not implement 845 LoopInfo(const LoopInfo &); // do not implement 846public: 847 static char ID; // Pass identification, replacement for typeid 848 849 LoopInfo() : FunctionPass(&ID) {} 850 851 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; } 852 853 /// iterator/begin/end - The interface to the top-level loops in the current 854 /// function. 855 /// 856 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator; 857 inline iterator begin() const { return LI.begin(); } 858 inline iterator end() const { return LI.end(); } 859 bool empty() const { return LI.empty(); } 860 861 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 862 /// block is in no loop (for example the entry node), null is returned. 863 /// 864 inline Loop *getLoopFor(const BasicBlock *BB) const { 865 return LI.getLoopFor(BB); 866 } 867 868 /// operator[] - same as getLoopFor... 869 /// 870 inline const Loop *operator[](const BasicBlock *BB) const { 871 return LI.getLoopFor(BB); 872 } 873 874 /// getLoopDepth - Return the loop nesting level of the specified block. A 875 /// depth of 0 means the block is not inside any loop. 876 /// 877 inline unsigned getLoopDepth(const BasicBlock *BB) const { 878 return LI.getLoopDepth(BB); 879 } 880 881 // isLoopHeader - True if the block is a loop header node 882 inline bool isLoopHeader(BasicBlock *BB) const { 883 return LI.isLoopHeader(BB); 884 } 885 886 /// runOnFunction - Calculate the natural loop information. 887 /// 888 virtual bool runOnFunction(Function &F); 889 890 virtual void releaseMemory() { LI.releaseMemory(); } 891 892 virtual void print(std::ostream &O, const Module* M = 0) const { 893 LI.print(O, M); 894 } 895 896 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 897 898 /// removeLoop - This removes the specified top-level loop from this loop info 899 /// object. The loop is not deleted, as it will presumably be inserted into 900 /// another loop. 901 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); } 902 903 /// changeLoopFor - Change the top-level loop that contains BB to the 904 /// specified loop. This should be used by transformations that restructure 905 /// the loop hierarchy tree. 906 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 907 LI.changeLoopFor(BB, L); 908 } 909 910 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 911 /// list with the indicated loop. 912 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 913 LI.changeTopLevelLoop(OldLoop, NewLoop); 914 } 915 916 /// addTopLevelLoop - This adds the specified loop to the collection of 917 /// top-level loops. 918 inline void addTopLevelLoop(Loop *New) { 919 LI.addTopLevelLoop(New); 920 } 921 922 /// removeBlock - This method completely removes BB from all data structures, 923 /// including all of the Loop objects it is nested in and our mapping from 924 /// BasicBlocks to loops. 925 void removeBlock(BasicBlock *BB) { 926 LI.removeBlock(BB); 927 } 928 929 static bool isNotAlreadyContainedIn(const Loop *SubLoop, 930 const Loop *ParentLoop) { 931 return 932 LoopInfoBase<BasicBlock, Loop>::isNotAlreadyContainedIn(SubLoop, 933 ParentLoop); 934 } 935}; 936 937 938// Allow clients to walk the list of nested loops... 939template <> struct GraphTraits<const Loop*> { 940 typedef const Loop NodeType; 941 typedef LoopInfo::iterator ChildIteratorType; 942 943 static NodeType *getEntryNode(const Loop *L) { return L; } 944 static inline ChildIteratorType child_begin(NodeType *N) { 945 return N->begin(); 946 } 947 static inline ChildIteratorType child_end(NodeType *N) { 948 return N->end(); 949 } 950}; 951 952template <> struct GraphTraits<Loop*> { 953 typedef Loop NodeType; 954 typedef LoopInfo::iterator ChildIteratorType; 955 956 static NodeType *getEntryNode(Loop *L) { return L; } 957 static inline ChildIteratorType child_begin(NodeType *N) { 958 return N->begin(); 959 } 960 static inline ChildIteratorType child_end(NodeType *N) { 961 return N->end(); 962 } 963}; 964 965template<class BlockT, class LoopT> 966void 967LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB, 968 LoopInfoBase<BlockT, LoopT> &LIB) { 969 assert((Blocks.empty() || LIB[getHeader()] == this) && 970 "Incorrect LI specified for this loop!"); 971 assert(NewBB && "Cannot add a null basic block to the loop!"); 972 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); 973 974 LoopT *L = static_cast<LoopT *>(this); 975 976 // Add the loop mapping to the LoopInfo object... 977 LIB.BBMap[NewBB] = L; 978 979 // Add the basic block to this loop and all parent loops... 980 while (L) { 981 L->Blocks.push_back(NewBB); 982 L = L->getParentLoop(); 983 } 984} 985 986} // End llvm namespace 987 988#endif 989